1. Field of the Invention
The invention concerns a method of operating a mill train for rolling strip-like rolling stock with an edger and a number of roll stands arranged one behind the other in a rolling direction, each of which has an adjusting unit for affecting the contour of the strip trailing end of rolling stock. The invention also concerns a mill train of this type, which, in particular, is also provided with an edger at the run-in end for width reduction of the rolling stock.
2. Description of the Related Art
A number of roll stands can be used in a mill train for rolling a rolling stock. The roll stands, which are usually designed as so-called multiple roll stands and comprise a number of work rolls and, if necessary, a number of backup rolls, are provided for passing through a usually very elongated rolling stock and are arranged one behind the other in the direction of advance of the rolling stock, which is also known as the rolling direction. A mill train with several roll stands of this type can be used especially in the working of a strip-like rolling stock or rolling strip. The strip-like rolling stock is formed in this case in the manner of a chiefly two-dimensional shape as rolling stock that is extended in a broad plane with a very small thickness relative to its dimensions in the extended plane.
Precisely in the working of rolling stock formed with this type of strip-like shape, the so-called strip flow, i.e., the passage of the rolling stock through the roll stands, is especially important. Specifically, during the working of the strip-like rolling stock, a tension develops within the rolling stock, which is also called strip tension. In this regard, the strip tension usually has a stabilizing effect on the actual strip flow. However, during working that is asymmetric with respect to the longitudinal central axis of the strip, the strip tension can also develop eccentrically. Consequently, deflection of the strip to the side may occur, for example, as the strip emerges from the rear roll stand as viewed in the rolling direction. Moreover, in the case of forces acting eccentrically on the rolling stock due to the strip tension, behavior of the strip trailing end that differs from that of the actual rolling stock can develop, which in turn can lead to rolling defects.
To be able to suitably control the strip flow, which is thus relevant to the rolling result, or the passage of the strip-like rolling stock through the roll stands, the roll stands can be designed in such a way that each roll stand is able to swivel about an axis of rotation that is essentially perpendicular to the rolling direction. By suitable swiveling of one or each roll stand, the strip flow can be affected in such a way that asymmetrically developing tensile stresses can be kept especially low, or in such a way that some other preset condition for the strip flow is maintained. Errors in the strip flow, which can result, for example, in defectively rolled strip trailing ends and damage to the rolls, which in turn can require additional roll changes, are usually corrected by suitable swiveling of the roll stands by an attendant. However, possible interventions with respect to achieving an especially good rolling result are limited, since, especially in the front roll stands as viewed in the rolling direction, necessary corrective measures are difficult to determine due to the still comparatively thick rolling stock present there, and since, in addition, the intervals between adjacent roll stands as viewed in the rolling direction are also comparatively difficult to inspect.